The present invention is particularly concerned with improvements in instant optical character set readers of the type shown in U.S. Pat. Nos. 4,282,425 and 4,570,057. The disclosures of these United States Patents are incorporated herein by reference by way of background.
The instant type of bar code reader with flashable illuminator means has proved to be extremely desirable for portable applications because of its unique simplicity and compact design. A significant goal of the present invention is to retain the major advantages of the present commercial instant readers with flashable illuminator means while enhancing the capacity for reading optical information sets of substantially greater dimesnion. An important related aspect of the invention is to enable the reading of such information sets by illuminating the same with an instantaneous flash of light while the information sets are at a greater distance from the frontal end of the reader. A further development goal is to more effectively adapt the reading operation both to close up information sets of high reflectivity and to labels at greater distances and of curved configuration.
The present invention is therefore particularly directed to the provision of an instant bar code reader which, while retaining the advantages of simplicity, ease of hand operation and ruggedness, achieves enhanced versatility by its ability to read optical information sets of greater length and multiple dimensions and to adapt to a greater range of reading distances. Such enhanced versatility is realized by providing the reader with an automatically controlled lens system and operating such control in accordance with a measure of reading distance. Further improvements are achieved by monitoring an average of reflected light from the bar code during a reading operation, and terminating integration of the reflected light from a bar code after an optimum measurement sample of the reflected light image has been received.
Aiming of the reader may be carried out with the assistance of visible marker light beams directed into the field of view of the reflected light image sensor. In an ideal embodiment, the marker beams extend from opposite ends of the information set image sensor through the reflected light optics so that the beams delineate the desired locations for the opposite ends of an information set in the reader field of view.
For the sake of energy conservation during portable operation, automatic control of the lens system may be disabled until such time as the information set is within an effective reading range. Where a capacitor discharge energizes a flashable illuminator, the capacitor discharge current may be interrupted as soon as an adequate amount of reflected light has been received; this not only reduces battery drain but also speeds up the capacitor recharging cycle: By monitoring the charge on the capacitor, a new reading cycle can be initiated after a minimum time lapse, should an initial reading cycle be unsuccessful. Accordingly, it is an object of the invention to provide an information set reader configuration particularly suited to hand held operation while exhibiting increased versatility.
A more specific object is to provide an information set reader capable of reading a wider range of information sets of varying types without sacrifice of essential simplicity and ease in hand held operation.
Another object is to provide an information set reader capable of rapid and efficient alignment with information sets located at substantial distances from the reader.
A further object of the invention is to provide an instant information set reader which achieves the foregoing objects while minimizing energy consumption so as to retain a capacity for extended portable operation.
A feature of the invention resides in the provision of an adaptive bar code image sensor system enabling a succession of readings of a given information set with reflected light from respective different segments of such information set controlling respective integration times. This feature is applicable, for example, to information sets on curved substrates such that an information set reading with a single integration time would not effectively sample reflected light from all segments of the label.
Further features leading to enhanced adaptability of the code image sensor system comprise individually operable flash illumination means enabling more rapid flash sequences, and/or enabling improved illumination of irregular or curved code configurations and/or of code configurations of greater extent, and/or enabling respective individually controlled flash durations immediately following each other, and e.g. adapted to respective different segments of a code configuration.
Still further features of an adaptive code image sensor system relate to simultaneous reading of code segments at markedly different depths of field and/or multiple depth measurement sensors for assessing the depth of respective segments of a code configuration, and/or selectable range, distance to image sensors effectively adapted to read code configurations at respective overlapping ranges for instantaneous adaptation to a code configuration at any range, distance over a wide range without the use of moving parts. In one implementation, the effective usable range of a lens system is greatly increased by providing multiple optical image paths of respective different lengths in the reader which lead through the lens system to respective independently controllable image sensors.
Another feature resides in the provision of a marker beam indicator system for delineating the optimum location for an information set in the reader field of view so that the reader can be positioned rapidly and efficiently even while at substantial distances from an optically readable information set. Various method features will be apparent from the following disclosure. For example, in a case where a curved bar code label (or other optically readable information set) has a central segment within the focal depth of the lens system, but the marginal segments are actually outside the focal depth, one exemplary method of programmed operation may provide for a second flash automatically after the lens system has automatically focused at a selected greater depth. By assembling the two readings, e.g. pixel by pixel, a good reading may be obtained with, e.g., valid start and stop characters being obtained from the second reading. In another method of programmed operation, a display forming part of the operator input/output means can instruct the operator to take first a reading of the left hand portion of a severely curved label, then a central portion and then a right hand portion, with the processor assembling the pixels of the respective readings to obtain a complete bar code image reading.
The operator could, in another mode, advise the reader processor, e.g., by the selective actuation of function keys or the like, of a particular reading sequence to be input to the reader processor for extremely long or sharply curved labels. The function keys could be part of a keyboard associated with the reader itself and/or a keyboard associated with a host computer unit directly mechanically coupled with the reader housing, or coupled via any suitable remote linkage means such as a cable or a radio frequency channel. In certain instances, the reader processor may assemble the pixels of successive readings not only with the assistance of internal check characters and preknowledge of code formats and the like and/or of specific reading sequences, but further with the assistance of measurements from multiple distance measurement sensors defining the general bar code spacial configuration. Utilizing multiple flashable illuminators and/or multiple intensity sensors may enable valid reading of different segments while avoiding in all cases, any saturation of CCD charge wells or the like of an image sensor. Saturation of any part of a CCD shift register may adversely affect subsequent operation of an image sensor.